1. Field of the Invention
The present invention relates to photography and, more particularly, to a camera accessory for light shielding a film unit that has been advanced through a film exit slot in the camera and at least partially extends outside of the camera housing.
2. Description of the Prior Art
The SX-70 Land Camera, marketed by Polaroid Corporation, Cambridge, Mass., is a highly automated, folding, self-developing camera which exposes and processes "integral type" self-developing film units.
One type of integral film unit which may be used in the SX-70 camera is disclosed in U.S. Pat. No. 3,647,437. The film unit provides a reflection print and includes a self-contained opacification system in the fluid processing composition which allows the film unit to be advanced, through a film exit slot in the camera, directly into the ambient illumination without causing further exposure of the photosensitive materials within the film unit.
Other integral type of self-developing film units have been proposed which either do not include a self-contained opacification system or includes an opacification for only one side of the photosensitive emulsion. Such film units (either reflection print or transparencies) must therefore be maintained in a light-free environment for a short imbibition period for, following distribution of a fluid processing composition within the film unit to prevent further exposure or fogging.
The present invention is directed to an accessory which may be readily attached to a commercially available SX-70 for providing a light-free environment when integral-type film units requiring the same are used therewith.
Without the addition of an accessory dark chamber or film unit light shield thereto, commercially available SX-70 cameras are adapted to expose and process self-developing film units which include a self-contained opacification system.
Subsequent to exposure, such a film unit is advanced between a pair of camera mounted pressure-applying rollers which rupture a pod or container on the film unit holding a fluid processing composition and distribute the fluid between a predetermined pair of layers of the film unit to initiate a development and diffusion transfer process.
Extending forwardly of the rollers is a camera housing section having a film exit slot in a bottom wall portion thereof. Intermediate the exit slot and the exit side of the rollers is a baffle or plate which is pivotally mounted on the bottom walls of the housing section, adjacent the exit slot, and is movable between a folded position wherein the plate is located in substantially parallel overlying relationship to the interior surface of the bottom wall and a normal extended position wherein the plate is inclined at approximately a 45-degree angle to the bottom wall and cooperates with side walls of the housing section and another camera housing section extending forwardly over the top of the rollers to form a lighttight chamber between the exit side of the rollers and the film exit slot. The length of the chamber is shorter than the length of the film unit.
In operation, the film unit advances through the pair of rollers and the leading edge of the film unit engages the erected baffle which deflects or gently bends the film unit from its normal path of travel and guides it to the film exit slot in the bottom wall where it emerges from the camera.
The baffle serves two functions. First, it provides a light-free environment between the rollers and film exit slot so that light rays may not impinge a transparent exposure and viewing "window" of the film unit and be transmitted, within the confines of a transparent sheet forming the window, rearwardly to that portion of the film unit on the entrance side of the rollers that has not as yet been covered by the processing fluid having the opacification system therein. The second function of the baffle relates to improving the uniformity of fluid distribution within the film unit. It has been found that by inducing a gentle bend in the film unit as it emerges from the rollers, substantial improvement in reliably obtaining uniform and complete coverage of the photo-exposed area of the film unit is achieved.
For a more detailed explanation of the construction and operation of the baffle, reference may be had to U.S. Pat. No. 3,810,211.
When the trailing end of the film unit has passed through the rollers, approximately one half of the image forming area of the film unit extends outside of the camera beyond the film exit slot. The film unit may be removed immediately however since it is protected from further exposure by the opacification system in the processing fluid.
The relatively short dark chamber extending between the pressure-applying rollers and the film exit slot is not adequate however to protect film units which do not include a self-container light opacification system (including reflection print and transparency film units) because the entire photosensitive or image-forming area of the film unit will not fit into the chamber.
The prior art is replete with self-developing cameras that include full length dark chambers or light shields in front of the pressure-applying rollers and/or film exit slots for receiving self-developing film units of the type which require a short imbibition period in a light-free environment subsequent to the distribution of the fluid processing composition.
Representative examples of such prior art may be found in U.S. Pat. Nos. 2,451,820; 2,467,320; 2,616,804; 3,369,469; 3,650,188; 3,678,830; and 3,748,990. Also see patent applications Ser. Nos. 466,371, (now U.S. Pat. No. 3,940,774) and 466,414 (now U.S. Pat. No. 3,938,167) filed May 2, 1974, Ser. No. 569,761, filed Apr. 21, 1975 and Ser. No. 569,751 filed Apr. 21, 1975 and now abandoned and replaced by copending continuing application Ser. No. 679,048 filed Apr. 21, 1976.
The dark chambers disclosed in the above patents and applications take a variety of forms. Some are rigid. Others fold or are extensible and retractable. Some of the chambers are permanently mounted on the camera housing, others are in the form of an accessory that is adapted to be detachably mounted on the camera.
All of the above have one common characteristic however. The camera and dark chamber have corresponding means thereon for operatively mounting the dark chamber on the camera.
Copending application Ser. No. 569,751, filed on Apr. 21, 1975 (and now abandoned and replaced by copending continuing application Ser. No. 679,048 filed Apr. 21, 1976), is directed to a dark chamber accessory that is adapted to be mounted on an SX-70 camera without having to make any modifications to the camera even though commercially available SX-70 cameras do not have specifically designed dark chamber mounting or coupling means thereon.
The dark chamber accessory is designed to fit into the forward housing section of the SX-70 camera in front of the pressure-applying rollers. To accommodate the accessory however the baffle plate is deflected to its folded position and blocks the film exit slot. Therefore, the existing baffle plate and film exit slot are not used and functional equivalents of these two camera elements must be built into the dark chamber accessory. This in turn causes the dark chamber accessory to be rather bulky which may provide the user with a mirror inconvenience in carrying or storing the adapter when it is not attached to the camera.